ci(mergify): upgrade configuration to current format #1889

Job	Run time
build_test_container	3m 53s
Confirm that codegen C++ passes tests with CWL	1m 7s
Schema Salad release test	11m 25s
CI tests via Tox (3, 9)	8m 50s
CI linters via Tox (lintreadme)	29s
CI tests via Tox (3, 10)	8m 57s
Confirm that codegen typescript passes tests with CWL	44s
CI linters via Tox (pydocstyle)	19s
CI tests via Tox (3, 11)	8m 10s
CI tests via Tox (3, 12)	9m 14s
CI tests via Tox (3, 13)	4m 2s
	57m 10s

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